A light emitting diode is a electroluminescence device having a structure in that an n-type semiconductor of which major carriers are electrons and a p-type semiconductor of which major carriers are holes are joined together, and emits predetermined light through recombination of these electrons and holes. Such light emitting diodes are used as display devices and backlights, and their application area has expanded to general illumination while substituting the conventional incandescent bulbs and fluorescent lamps.
A light emitting diode consumes less electric power and has a longer service life as compared with conventional light bulbs or fluorescent lamps. The electric power consumption of a light emitting diode is less than a few tenths to a few hundredths of that of conventional illumination devices, and the life span thereof is several to several ten times, thereby having reduced electric power consumption and excellent durability.
However, the light emitting diode is repeatedly turned on and off depending on the direction of a current. Therefore, if the light emitting diode is used while being connected directly to an AC power source, there is a problem in that the light emitting diode may be easily damaged. Accordingly, it is difficult to use a light emitting diode for the purpose of general illumination by connecting it directly to a household AC power source.